Preparation method and application of a bio-based adhesive based on double dynamic covalent bonds for enhancing and toughening

Abstract

The present application relates to the technical field of bio-based formaldehyde-free adhesive, and aims to provide a preparation method of high-strength and high-toughness bio-based adhesive and application thereof. The present application constructs a boron nitride nanosheet based on thiol click chemistry functional modification through interface molecular structure design, innovates interface mechanical interlocking and chemical multi-network crosslinking reinforcement and toughening integrated technology, provides a preparation method of boron nitride nanosheet intercalation modification of plant protein adhesive, significantly improves the poor interfacial adhesion of the adhesive and the wood surface, and obtains a bio-based adhesive with good water resistance, high strength, excellent toughness and wider application range. The high-performance, high-strength and high-toughness bio-based adhesive prepared by the present application has a dry shear strength of 2.56 MPa, a wet shear strength of 1.32 MPa and a wet debonding work of 1800 mJ when hot-pressed into plywood, showing excellent strength and toughness, and the thermal stability and flame retardance of the adhesive are significantly enhanced, which has a broad industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-based formaldehyde-free adhesive, in particular to a preparation method and application of a high-performance high-strength high-toughness bio-based adhesive. BACKGROUND

[0002] The formaldehyde-free protein-based adhesive can solve the problem of formaldehyde pollution in the human living environment caused by wood-based panels and their products and the problem of dependence on fossil resources for wood adhesive raw materials. Therefore, with the improvement of people's environmental protection consciousness and the pursuit of high-quality life, formaldehyde-free protein-based adhesives are increasingly valued in the field of wood science and technology research and in the production of wood-based panels. Among them, plant protein adhesives show great development potential due to their abundant raw materials, low price, and environmental friendliness and convenience in production, transportation, and use. However, traditional plant protein adhesives have hard and brittle cured adhesive layers and poor adhesive interface bonding, resulting in low dry bonding strength of adhesive products such as wood-based panels and poor impact resistance of the adhesive interface, which often causes problems such as delamination and deformation during actual production and application, and easy chipping during sawing, limiting the further application and promotion of plant protein adhesives. Therefore, improving the strength and toughness of the cured adhesive layer of plant protein adhesives is of great significance and research value for developing high-performance high-strength high-toughness plant protein adhesives. SUMMARY

[0003] The present application overcomes the problems of poor water resistance of ordinary plant protein adhesives, large brittleness of the cured adhesive layer after cross-linking modification, and easy chipping during sawing in the actual production and application of plywood in the wood-based panel industry, and aims to provide a preparation method and application of a high-performance high-strength high-toughness plant protein adhesive. The present application provides a preparation method for modifying and reinforcing a plant protein adhesive by intercalating boron nitride nanosheets through interface molecular structure design and construction of a boron nitride nanosheet based on thiol click chemistry functional modification, innovative interface mechanical interlocking and chemical multi-network cross-linking reinforcement and toughening integration technology, which significantly improves the poor interfacial adhesion of the adhesive and the wood surface, and obtains a bio-based adhesive with good water resistance, high strength, excellent toughness, and a wider application range. The thermal stability and flame retardance of the adhesive are significantly enhanced, and the adhesive has a broad industrial application prospect.

[0004] TECHNICAL PROBLEM SOLVED

[0005] In view of the problems of poor water resistance of ordinary plant protein adhesives, large brittleness of the cured adhesive layer after cross-linking modification, and easy chipping during sawing in the actual production and application of plywood in the wood-based panel industry, the present application provides a preparation method for modifying and reinforcing a plant protein adhesive by intercalating boron nitride nanosheets through interface molecular structure design and construction of a boron nitride nanosheet based on thiol click chemistry functional modification, innovative interface mechanical interlocking and chemical multi-network cross-linking reinforcement and toughening integration technology, which significantly improves the poor interfacial adhesion of the adhesive and the wood surface, and obtains a bio-based adhesive with good water resistance, high strength, excellent toughness, and a wider application range. The thermal stability and flame retardance of the adhesive are significantly enhanced, and the adhesive has a broad industrial application prospect.

[0006] TECHNICAL SCHEME

[0007] In view of the deficiencies of the prior art, the present application provides the following technical solutions: a boron nitride nanosheet based on thiol click chemistry functional modification to enhance and toughen a bio-based adhesive, the high-performance high-strength high-toughness plant protein adhesive is made of the following components: soybean meal, water, functionally modified boron nitride nanosheet, epoxy crosslinking agent, catalyst;

[0008] The preparation method of the present application utilizes the functionally modified boron nitride nanosheet to form a stable mechanical interlocking structure with the plant protein matrix, and can also form covalent / non-covalent interaction with the plant protein matrix, thereby forming a firm physical locking and multiple chemical crosslinking network structure, which is beneficial to improve the bonding strength and toughness of the plant protein adhesive.

[0009] The preparation method of the high-performance high-strength high-toughness plant protein adhesive is as follows:

[0010] (1) Preparation of functionally modified boron nitride nanosheet. The specific steps are as follows: hexagonal boron nitride, isopropyl alcohol and deionized water are stirred and mixed uniformly, and hydroxylated boron nitride nanosheet is obtained by ultrasonic assisted liquid phase exfoliation, which is well dispersed in aqueous solution to form a colloidal solution, then (3-mercaptopropyl) trimethoxysilane is added to the above colloidal solution by improved sol-gel technology, and heated to reflux. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain thiol functionalized boron nitride nanosheet.

[0011] (2) Preparation of high-performance high-strength high-toughness plant protein adhesive. To ensure the dispersibility of thiol functionalized boron nitride nanosheet in soybean meal matrix, first, thiol functionalized boron nitride nanosheet is added to water and stirred uniformly, then ultrasonic is performed to make it uniformly dispersed. The soybean meal matrix is pretreated with 2-mercaptoethanol to expose more thiol groups. Then, an appropriate amount of crosslinking agent and pretreated soybean meal are added to the reaction container and stirred uniformly, then citric acid is added and continues to be stirred to promote the formation of disulfide bonds between the protein chains and thiol boron nitride nanosheet in the adhesive, and a thiol functionalized boron nitride nanosheet modified plant protein adhesive sample is prepared.

[0012] Preferably, the mass ratio of hexagonal boron nitride, isopropyl alcohol and deionized water in step (1) is 1-5:10-50:50-200.

[0013] Preferably, the ultrasonic assisted liquid phase exfoliation time in step (1) is 1-10h.

[0014] Preferably, the mass ratio of (3-mercaptopropyl) trimethoxysilane to colloidal solution in step (1) is 1-10:80-150.

[0015] Preferably, the heating reflux temperature in step (1) is 80-150℃, and the time is 0.5-3h.

[0016] Preferably, the hexagonal boron nitride in step (1) can be one or more of graphene, graphene oxide, molybdenum disulfide, tungsten disulfide, boron nitride, mica, hydrotalcite.

[0017] Preferably, the mass ratio of the soybean meal matrix to 2-mercaptoethanol in step (2) is 20-50:1-5.

[0018] Preferably, the amount of crosslinking agent added in step (2) is 1-10% of the mass of the adhesive.

[0019] Preferably, the amount of citric acid added in step (2) is 0.1-5% of the mass of the adhesive.

[0020] Preferably, the mass ratio of soybean meal, mercapto-functionalized boron nitride nanosheets, and dispersion medium water in step (2) is 10-30:0.001-0.01:30-100.

[0021] Preferably, the soybean meal matrix in step (2) can be one or more of low-temperature soybean meal, high-temperature soybean meal, peanut meal, rapeseed meal, high-temperature cottonseed meal, and low-temperature cottonseed meal.

[0022] Preferably, the crosslinking agent in step (2) is one or more of ethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, bisphenol A diglycidyl ether, and epoxy hyperbranched polymer.

[0023] Preferably, the citric acid in step (2) can be one or more of citric acid, caffeic acid, gallic acid, and tartaric acid.

[0024] Beneficial technical effects

[0025] Compared with the prior art, the present application has the following beneficial technical effects:

[0026] 1. The high-performance high-strength high-toughness plant protein adhesive developed by the present application is based on the thiol-epoxy "click" chemistry, amino-epoxy, and dynamic disulfide bond multi-network synergistic effect. The functionally modified boron nitride nanosheets can form a stable mechanical interlocking structure and enhanced covalent / non-covalent interaction with the plant protein matrix, which is beneficial to stress transfer and energy dissipation in the adhesive system, and endows the plant protein adhesive with excellent bonding strength and toughness, good environmental benefits, economic benefits, and good industrial application prospects.

[0027] 2、Traditional plant protein adhesive mixed with boron nitride nanosheets can improve the performance of the adhesive, but the practical application of boron nitride nanosheets is still limited by its high surface energy and strong aggregation tendency. The physicochemical properties of boron nitride nanosheets are completely different from those of the plant protein matrix, and the compatibility and strong interfacial adhesion between the two are not good. If boron nitride nanosheets are simply physically mixed with plant protein, phase separation and other problems will occur, which will prevent boron nitride nanosheets from playing a role in enhancing and toughening plant protein adhesives. The present application promotes the uniform dispersion of boron nitride nanosheets in plant protein adhesives by appropriate functionalization, and increases their interfacial interaction, thereby improving mechanical, thermal and electrochemical properties and promoting the further application of plant protein adhesives.

[0028] 3、The present application uses low-cost and green agricultural and forestry waste soybean meal as the raw material of the adhesive, and boron nitride nanosheets as the reinforcing agent, which is conducive to the full utilization of agricultural and forestry waste resources, alleviates the problem of shortage of petrochemical resources caused by traditional formaldehyde-based adhesives, and conforms to the concept of sustainable development; in addition, the plant protein adhesive does not release formaldehyde and other problems, solving the problem of organic volatile matter and formaldehyde harm to human health and environmental pollution caused by traditional wood-based panels.

[0029] 4、The process of ordinary modified bio-based adhesive is relatively complicated, and the cured adhesive layer is hard and brittle. The process of the present application is simple, the bonding strength is high, the water resistance is good, and the flame retardant performance and mildew resistance performance of the bio-based adhesive are also improved, solving the problems of the prior art CN118562443A and CN118222244A, such as large amount of filler addition, high cost, low bonding strength, hard and brittle cured adhesive layer, complex production process, and harsh reaction conditions. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 and Figure 2 The bonding strength of the high-strength and high-toughness plant protein adhesive obtained by the examples and the control examples in the present application. DETAILED DESCRIPTION

[0031] The experimental methods used in the following examples are conventional operation methods unless otherwise specified.

[0032] Overall scheme:

[0033] A high-performance high-strength and high-toughness plant protein adhesive is made from the following ingredients: soybean meal, water, functionally modified boron nitride nanosheets, epoxy crosslinking agent, and catalyst.

[0034] Example 1

[0035] A modified plant protein adhesive comprises the following steps:

[0036] (1) Preparation of plant protein adhesive. 28 g of soybean meal was added to 72 g of water and stirred for 10 min until the solution was uniform and stable. 4 g of ethylene glycol diglycidyl ether was added to the system and continued to stir for 10 min to obtain the modified plant protein adhesive.

[0037] (2) Preparation of three-layer poplar plywood and test its performance, the results are listed in Figure 1 and Figure 2 .

[0038] Example 2

[0039] A high-performance high-strength high-toughness plant protein adhesive, comprising the following steps:

[0040] (1) Preparation of functionally modified boron nitride nanosheets. 5 g of hexagonal boron nitride was mixed with 100 g of isopropyl alcohol and deionized water and stirred uniformly, and then ultrasonic-assisted liquid phase exfoliation was used to obtain hydroxylated boron nitride nanosheets, which were well dispersed in aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl) trimethoxysilane was added to the above colloidal solution by using a modified sol-gel technique, and heated to reflux at 90°C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets with a mercapto grafting rate of 0.1%.

[0041] (2) Preparation of high-performance high-strength high-toughness plant protein adhesive. To ensure the dispersibility of mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.1 g of mercapto-functionalized boron nitride nanosheets was added to 72 g of water and stirred uniformly, and then ultrasonic treatment was performed for 0.5 h to ensure uniform dispersion. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction container containing mercapto-functionalized boron nitride nanosheets and stirred uniformly, and then 0.3 g of citric acid was added to continue stirring to promote the formation of disulfide bonds between the protein chains and the mercapto boron nitride nanosheets in the adhesive, and a sample of mercapto-functionalized boron nitride nanosheet modified plant protein adhesive was prepared.

[0042] (3) Preparation of three-layer poplar plywood and test its performance, the results are listed in Figure 1 and Figure 2 .

[0043] Example 3

[0044] A high-performance high-strength high-toughness plant protein adhesive, comprising the following steps:

[0045] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was mixed with 100 g of isopropyl alcohol and deionized water by stirring, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation. The nanosheets were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl) trimethoxysilane was added to the colloidal solution by using a modified sol-gel technique, and the mixture was heated and refluxed at 90°C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, with a mercapto grafting rate of 0.1%.

[0046] (2) Preparation of high-performance high-strength high-toughness plant protein adhesive. To ensure the dispersibility of the mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, 0.3 g of the nanosheets was first added to 72 g of water and stirred uniformly, and then ultrasonicated for 0.5 h to ensure uniform dispersion. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of a crosslinking agent and 28 g of the pretreated soybean meal were added to the reaction vessel containing the mercapto-functionalized boron nitride nanosheets, and the mixture was stirred uniformly. 0.3 g of citric acid was then added to promote the formation of disulfide bonds between the protein chains and the mercapto boron nitride nanosheets in the adhesive, and a sample of mercapto-functionalized boron nitride nanosheet-modified plant protein adhesive was prepared.

[0047] (3) Three-layer poplar plywood was prepared and its performance was tested, and the results are shown in Figure 1 and Figure 2 .

[0048] Example 4

[0049] A high-performance high-strength high-toughness plant protein adhesive, comprising the following steps:

[0050] (1) Preparation of functionalized boron nitride nanosheets. 5 g of hexagonal boron nitride was mixed with 100 g of isopropyl alcohol and deionized water by stirring, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid-phase exfoliation. The nanosheets were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl) trimethoxysilane was added to the colloidal solution by using a modified sol-gel technique, and the mixture was heated and refluxed at 90°C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, with a mercapto grafting rate of 0.1%.

[0051] (2) High performance high strength and high toughness plant protein adhesive preparation. To ensure the dispersibility of the thiol-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.5 g of thiol-functionalized boron nitride nanosheets was added to 72 g of water and stirred uniformly, and then ultrasonic was performed for 0.5 h to make it uniformly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more thiol groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction container containing thiol-functionalized boron nitride nanosheets and stirred uniformly, and then 0.3 g of citric acid was continuously added and stirred to promote the formation of disulfide bonds between the protein chains and the thiol boron nitride nanosheets in the adhesive, and a thiol-functionalized boron nitride nanosheet modified plant protein adhesive sample was prepared.

[0052] (3) Three-layer poplar plywood was pressed, and its performance was tested, and the results are listed in Figure 1 and Figure 2 .

[0053] Example 5

[0054] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0055] (1) Preparation of functionally modified boron nitride nanosheets. 5 g of hexagonal boron nitride was mixed with 100 g of isopropyl alcohol and deionized water, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid phase exfoliation. The nanosheets were well dispersed in the aqueous solution to form a colloidal solution. Subsequently, 0.5 g of (3-mercaptopropyl) trimethoxysilane was added to the colloidal solution by improved sol-gel technology, and refluxed at 90°C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain thiol-functionalized boron nitride nanosheets with a thiol grafting rate of 0.3%.

[0056] (2) High performance high strength and high toughness plant protein adhesive preparation. To ensure the dispersibility of the thiol-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.5 g of thiol-functionalized boron nitride nanosheets was added to 72 g of water and stirred uniformly, and then ultrasonic was performed for 0.5 h to make it uniformly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more thiol groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction container containing thiol-functionalized boron nitride nanosheets and stirred uniformly, and then 0.3 g of citric acid was continuously added and stirred to promote the formation of disulfide bonds between the protein chains and the thiol boron nitride nanosheets in the adhesive, and a thiol-functionalized boron nitride nanosheet modified plant protein adhesive sample was prepared.

[0057] (3) Three-layer poplar plywood was pressed, and its performance was tested, and the results are listed in Figure 1 and Figure 2 .

[0058] Example 6

[0059] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0060] (1) Preparation of functionally modified boron nitride nanosheets. 5 g of hexagonal boron nitride is stirred and mixed uniformly with 100 g of isopropyl alcohol and deionized water, and hydroxylated boron nitride nanosheets are obtained by ultrasonic-assisted liquid phase exfoliation, which are well dispersed in aqueous solution to form a colloidal solution. Subsequently, 1 g of (3-mercaptopropyl) trimethoxysilane is added to the above colloidal solution by using a modified sol-gel technique, and heated to reflux at 90°C for 0.5 h. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, with a mercapto grafting rate of 0.5%.

[0061] (2) Preparation of high-performance high-strength and high-toughness plant protein adhesive. To ensure the dispersibility of the mercapto-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of mercapto-functionalized boron nitride nanosheets is stirred uniformly in 72 g of water and then ultrasonicated for 0.5 h to make it uniformly dispersed. 100 g of soybean meal matrix is pretreated with 10 g of 2-mercaptoethanol to expose more mercapto groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal are added to the reaction container containing the mercapto-functionalized boron nitride nanosheets, stirred uniformly, and then 0.3 g of citric acid is added to continue stirring to promote the formation of disulfide bonds between the protein chains and the mercapto boron nitride nanosheets in the adhesive, and a sample of plant protein adhesive modified by mercapto-functionalized boron nitride nanosheets is prepared.

[0062] (3) Pressing of three-layer poplar plywood, and testing of its performance, with the results listed in Figure 1 and Figure 2 .

[0063] Example 7

[0064] A high-performance high-strength and high-toughness plant protein adhesive, comprising the following steps:

[0065] (1) Preparation of functionally modified boron nitride nanosheets. 5 g of hexagonal boron nitride is stirred and mixed uniformly with 100 g of isopropyl alcohol and deionized water, and hydroxylated boron nitride nanosheets are obtained by ultrasonic-assisted liquid phase exfoliation, which are well dispersed in aqueous solution to form a colloidal solution. Subsequently, 1.5 g of (3-mercaptopropyl) trimethoxysilane is added to the above colloidal solution by using a modified sol-gel technique, and heated to reflux at 90°C for 0.5 h. After cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheets, with a mercapto grafting rate of 1%.

[0066] (2) Preparation of high performance high strength and high toughness plant protein adhesive. To ensure the dispersibility of the thiol-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of thiol-functionalized boron nitride nanosheets was added to 72 g of water and stirred uniformly, and then ultrasonic was performed for 0.5 h to make it uniformly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more thiol groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction container containing thiol-functionalized boron nitride nanosheets and stirred uniformly, and then 0.3 g of citric acid was continuously added and stirred to promote the formation of disulfide bonds between the protein chains and the thiol boron nitride nanosheets in the adhesive, and a thiol-functionalized boron nitride nanosheet modified plant protein adhesive sample was prepared.

[0067] (3) Preparation of three-layer poplar plywood, test its performance, the results are listed in Figure 1 and Figure 2 .

[0068] Example 8

[0069] A high performance high strength and high toughness plant protein adhesive, comprising the following steps:

[0070] (1) Preparation of functionally modified boron nitride nanosheets. 5 g of hexagonal boron nitride was mixed with 100 g of isopropyl alcohol and deionized water, and hydroxylated boron nitride nanosheets were obtained by ultrasonic-assisted liquid phase exfoliation. The nanosheets were well dispersed in the aqueous solution to form a colloidal solution. Then, 2 g of (3-mercaptopropyl) trimethoxysilane was added to the colloidal solution by improved sol-gel technology, and refluxed at 90°C for 0.5 h. After cooling to room temperature, the mixture was washed with ethanol and filtered to obtain thiol-functionalized boron nitride nanosheets with a thiol grafting rate of 1.5%.

[0071] (2) Preparation of high performance high strength and high toughness plant protein adhesive. To ensure the dispersibility of the thiol-functionalized boron nitride nanosheets in the soybean meal matrix, first, 0.3 g of thiol-functionalized boron nitride nanosheets was added to 72 g of water and stirred uniformly, and then ultrasonic was performed for 0.5 h to make it uniformly dispersed. 100 g of soybean meal matrix was pretreated with 10 g of 2-mercaptoethanol to expose more thiol groups. Then, 2 g of crosslinking agent and 28 g of pretreated soybean meal were added to the reaction container containing thiol-functionalized boron nitride nanosheets and stirred uniformly, and then 0.3 g of citric acid was continuously added and stirred to promote the formation of disulfide bonds between the protein chains and the thiol boron nitride nanosheets in the adhesive, and a thiol-functionalized boron nitride nanosheet modified plant protein adhesive sample was prepared.

[0072] (3) Preparation of three-layer poplar plywood, test its performance, the results are listed in Figure 1 and Figure 2 .

[0073] Comparative Example 1

[0074] A plant protein adhesive comprising the following steps:

[0075] (1) Preparation of plant protein adhesive. 28 g of soybean meal was added to 72 g of water and stirred for 10 min until the solution was uniformly stable. Thus, the plant protein adhesive was obtained.

[0076] (2) Three-layer poplar plywood was pressed and its performance was tested, and the results are listed in Figure 1 and Figure 2 .

[0077] Comparative Example 2

[0078] A modified plant protein adhesive comprising the following steps:

[0079] (1) Preparation of plant protein adhesive. 28 g of soybean meal was added to 72 g of water and stirred for 10 min until the solution was uniformly stable. 4 g of trimethylolpropane triglycidyl ether was added to the system and stirred for another 10 min. Thus, the modified plant protein adhesive was obtained.

[0080] (2) Three-layer poplar plywood was pressed and its performance was tested, and the results are listed in Figure 1 and Figure 2 .

[0081] Comparative Example 3

[0082] A modified plant protein adhesive comprising the following steps:

[0083] (1) Preparation of plant protein adhesive. 28 g of soybean meal was added to 72 g of water and stirred for 10 min until the solution was uniformly stable. 0.5 g of unmodified boron nitride was added to the system and stirred for 10 min, and then 4 g of trimethylolpropane triglycidyl ether was added and stirred for another 10 min. Thus, the modified plant protein adhesive was obtained.

[0084] (2) Three-layer poplar plywood was pressed and its performance was tested, and the results are listed in Figure 1 and Figure 2 .

[0085] Comparative Example 4 (Patent Publication No. CN116622060B Example 1 technical solution)

[0086] The test results of the plywood are listed in Figure 1 and Figure 2 .

[0087] Comparative Example 5 (Patent Publication No. CN118222244A Example 1 technical solution)

[0088] The test results of the plywood are listed in Figure 1 and Figure 2 .

[0089] Comparative Example 6 (Patent Publication No.: CN118562443A Example 1 technical solution)

[0090] The test results of the plywood are shown in Figure 1 and Figure 2 .

[0091] The high-performance high-strength high-toughness plant protein adhesive prepared in Examples 1 to 8 and the adhesive prepared in Comparative Examples 1 to 6 were selected to prepare three-layer plywood with a moisture content of 5-15%, a size of 40cm*40cm*0.15cm, and according to the following process:

[0092] Gluing: double-sided gluing of the core board, with a glue application amount of 300-400g / m 2 ;

[0093] Pressing: pressure 1MPa, temperature 110-130℃, time 6 minutes.

[0094] The produced plywood products were detected for their bonding strength performance according to the detection method of GB / T17657-1999 "Experimental methods for physical and chemical properties of wood-based panels and veneered wood-based panels", and the detection results are shown in Figure 1 and Figure 2 .

[0095] As can be seen from Figure 1 and Figure 2 , the high-performance high-strength high-toughness plant protein adhesive described in the application is made of the following components: soybean meal, water, functionally modified boron nitride nanosheet, epoxy crosslinking agent, catalyst, by using the functionally modified boron nitride nanosheet to form a stable mechanical interlocking structure with the plant protein matrix, and also to form covalent / non-covalent action with the plant protein matrix, thereby forming a firm physical locking and multiple chemical crosslinking network structure, which is beneficial to improve the bonding strength and toughness of the plant protein adhesive. The test results show that the three-layer plywood pressed using the adhesive of the application has excellent mechanical properties, with a wet shear strength of 0.94-1.61MPa, and is superior to the comparative examples.

[0096] From Figure 1 and Figure 2 Figure 1 Figure 2 Figure 1 Figure 2It can be seen that the dry shear strength and wet shear strength of the plywood prepared by using the high-performance high-strength high-toughness plant protein adhesive prepared in Examples 1 to 4 are gradually improved. It can be seen that with the addition of the functionally modified boron nitride nanosheet, effective active sites can be generated, and strong interfacial interaction can be formed between the protein polymer and the nanosheet, thereby improving the dispersibility of the nanosheet in the adhesive. By utilizing the enhanced interfacial interaction and interfacial adhesion between the nanosheet and the plant protein, the toughening plant protein adhesive is synergistically enhanced, and the water-resistant bonding performance of the adhesive is improved.

[0097] Comparing Comparative Example 1, Example 2 and Examples 5, 6, 7, 8, the dry shear strength and wet shear strength of the adhesive are gradually improved. This is because the grafting rate of the functionally modified boron nitride nanosheet gradually increases, the generated active sites increase, the interfacial interaction between the protein and the nanosheet is stronger, the formation of a firm physical lock and a multiple chemical crosslinking network structure in the adhesive is promoted, and the water-resistant bonding performance of the adhesive is improved.

[0098] Compared with the prior art, the water-resistant bonding performance of the plywood prepared by using the functionally modified boron nitride nanosheet in the present application is significantly better than that of the prior art.

[0099] Therefore, the preparation method of the high-performance high-strength high-toughness plant protein adhesive of the present application is to use soybean meal, water, an epoxy crosslinking agent, a catalyst and other basic raw materials, and to use functionally modified boron nitride nanosheet to form a stable mechanical interlocking structure with the plant protein matrix and to form covalent / non-covalent interaction with the plant protein matrix, thereby forming a firm physical lock and a multiple chemical crosslinking network structure, to prepare a high-performance high-strength high-toughness plant protein adhesive with high strength and excellent performance, which has good industrial application prospects.

[0100] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A high-strength high-toughness plant protein adhesive, characterized by, It is composed of the following raw materials: soybean meal, water, functionally modified boron nitride nanosheet, epoxy crosslinking agent, catalyst; the preparation method of the functionally modified boron nitride nanosheet comprises the following steps: Hexagonal boron nitride is stirred and mixed uniformly with isopropanol and deionized water, and hydroxylated boron nitride nanosheet is obtained by ultrasonic-assisted liquid phase exfoliation, which is well dispersed in aqueous solution to form a colloidal solution, then (3-mercaptopropyl) trimethoxysilane is added to the above colloidal solution by using a modified sol-gel technology, and heated to reflux; after cooling to room temperature, the mixture is washed with ethanol and filtered to obtain mercapto-functionalized boron nitride nanosheet; The epoxy crosslinking agent is ethylene glycol diglycidyl ether; The catalyst is one or more of citric acid, coffee acid, gallic acid and tartaric acid.

2. The high-strength and high-toughness plant protein adhesive according to claim 1, characterized in that, The soybean meal is one or more of low-temperature soybean meal and high-temperature soybean meal.

3. The method according to claim 1, wherein the plant protein adhesive has high strength and high toughness. It comprises the following steps: In order to ensure the dispersibility of the mercapto-functionalized boron nitride nanosheet in the soybean meal matrix, first, the mercapto-functionalized boron nitride nanosheet is stirred and mixed uniformly in water, and then ultrasonic is performed to make it uniformly dispersed, the soybean meal matrix is pretreated with 2-mercaptoethanol to expose more mercapto groups, then a proper amount of crosslinking agent and pretreated soybean meal are added to the reaction container and stirred uniformly, and then citric acid is added and stirred to promote the formation of disulfide bonds between the protein chains in the adhesive and the mercapto boron nitride nanosheet, thus preparing a sample of mercapto-functionalized boron nitride nanosheet modified plant protein adhesive.

4. The use of the high-strength and high-toughness plant protein adhesive according to claim 1 in wood processing.

5. The use of the high-strength and high-toughness plant protein adhesive according to claim 1 in artificial board.

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